1. Field of the Invention
The invention relates to a method for the preparation of high modulus and high strength linear polycondensates for known commercial utility.
2. Prior Art
It is known that polymer materials subjected to external drawing pass into an oriented state characterized by improved physico-mechanical properties. Several methods for the preparation of highly oriented polymer materials are known, including:
1. Mechanical drawing below the melting temperature of the polymer (Cappacio, G., T. A. Crompton, I. M Ward, ASC Polym. Prepr., 18 (1977) 343). PA0 2. Extrusion from the melt (most often used in the production of industrial fibers) or solid state extrusion (Mead, W. T., R. S. Porter, Flow Induced Crystallization Symposium, Midland Macromolecular Institute, Michigan, August (1977)). PA0 3. Formations from solutions (which is the case with the polymer material KEVLAR.RTM.) (Ciferri and Ward, Ultra-High Modulus Polymers, Applied Science Publishers, London (1979) 203, 205-211). PA0 4. Two-stage orientation at high temperatures (Wilson, M. P. Polymer 15 (1974) 277).
The disadvantages of the known methods consist in that it is not possible to obtain at room temperature a draw ratio higher than 5-6:1 for polyamide 6 (PA-6), poly(ethyleneterephthalate) (PET) and poly(butyleneterephthalate) (PBT) and the higher orientation of these polymers at temperatures close to their melting points does not lead to a substantial increase in their strength. For this reason, the above cited methods are inapplicable to PA-6, PET and PBT since their chemical structure is different from and more complicated than that of the polyolefins, e.g., polyethylene, polypropylene, etc., used in the literature sources cited above.